As a developing method conducted in plate making of aqueous development type photosensitive resin plates, there has been known, for example, a method of spraying an aqueous developing solution comprising a surfactant as a main ingredient to a plate surface of a photosensitive resin plate after the completion of exposure and/or bringing a brush in contact with the plate surface by way of a developing solution to dissolve an uncured resin in a not-exposed area into the developing solution, thereby forming a relief image on the resin plate while leaving only the cured resin in an exposed area.
As a means for spraying an aqueous developing solution comprising the surfactant as the main ingredient to the plate surface of the photosensitive resin plate, spraying using a spray device is often used generally and, in addition, spraying of the developing solution using a paddle device or the like is also adopted.
In general, the spray device comprises a spray nozzle for spraying a developing solution to the plate surface of the photosensitive resin plate disposed above the liquid surface of a developer tank and a circulatory supply pump for supplying under circulation a developing solution in the developer tank to the spray nozzle.
In the existent developing method of the photosensitive resin plate adapted to blow the developing solution to the plate surface, the developing solution is degraded at a relatively small number of prepared plates, to result in the following disadvantages.
That is, the concentration of the uncured resin dissolved or dispersed in the developing solution increases up to 2 to 3% by weight at a relatively small cycles of development to lower the developing power of the developing solution, in which the uncured resin remained not being dissolved or dispersed in the developing solution is blown together with the developing solution by way of the circulatory supply pump from the spray nozzle to deposit again on the surface of the relief image, thereby degrading he image quality.
Further, while a defoamer such as silicone is added in a great amount into the developing solution of the developer tank with an aim of inhibiting generation of bubbles upon spraying the developing solution from the spray nozzle to the plate surface, an oil component contained in the silicone or the like is liberated and deposited on the plate surface and the deposited oil component repels the aqueous ink used for printing to lower the quality of the printed products.
Accordingly, in order to eliminate such drawbacks, the developing solution has been replaced at a relatively small number of prepared plates, but this not only results in lowering of the efficiency for the print making operation but also causes increase in the developing solution wastes.
Therefore, in the relevant field of art, it has been demanded for the technique capable of attaining the improvement for the efficiency of the plate making operation and decrease of the developing solution wastes by extending the life of the developing solution and increasing the number of prepared plates with a predetermined amount of the developing solution but, in order to cope with such a demand, it is necessary to minimize the oil component liberated from the defoamer such as silicone, as well as remove the uncured resin contained in the developing solution on the plate surface before the uncured resin is dissolved into the developing solution in the developer tank.
Referring more specifically, the uncured resin in the developing solution is dispersed by the function of an anionic and/or nonionic surfactant, but the uncured resin blown off the plate surface by a spray pressure upon spraying the developing solution on the plate surface is also dissolved in a not thoroughly dispersed state of oil droplets into the developing solution in the developer tank, which is blown together with the developing solution by way of the circulatory supply pump from the spray nozzle to the plate surface and re-deposited on the plate surface.
Further, referring to the defoamer, the defoamer itself tends to cause breakage of emulsion by the sharing force of an impeller of the circulatory supply pump upon passage through the impeller, so that the raw material such as silicone is liberated and suspended as oil spots in the developing solution. When they are spraying from the spray nozzle to the plate surface and deposited on the plate surface, they repel the aqueous ink used for printing and cause printing troubles.
Accordingly, it is necessary for extending the life of the developing solution to remove such uncured resin and oil spots, for example, of silicone before re-deposition on the plate surface.
As a method of removing the uncured resin or the oil component such as silicone in the developing solution, regeneration of the developing solution by distillation or filtration may be considered.
However, in the regeneration method for the developing solution by distillation under a reduced pressure, the resin component tends to adhere to a heat exchange section and, accordingly, it is necessary to previously remove a sludge-like resin component by flocculating precipitation or the like in order to prevent lowering of heat conduction efficiency in the heat exchange section, resulting in a problem that the handling of the resin is difficult.
Further, there is also a regeneration method for the developing solution using membranes such as ultra-filtration membrane, reverse osmotic membrane or ion exchange membrane. However, since the viscous uncured resin clogs the membrane, the membrane life is shortened and, accordingly, the resin component has to be removed previously by the flocculating precipitation or the like, which also results in a difficulty for the handling of the resin.
Further, in a so-called cartridge type filter of disposing a filter material as a cartridge in a developing solution supply pipe, the uncured resin in the developing solution passes through the mesh of the filter making it impossible to regenerate the developing solution.
The present invention has been accomplished in view of he background art as described above and it is an object hereof to provide a method of developing a photosensitive resin plate, as well as a developing apparatus capable of attaining the improvement for the efficiency in the plate making operation and decrease in the developing solution wastes, by minimizing an oil component liberating from a defoamer such as silicone and removing an uncured resin contained in the developing solution on the plate surface before the uncured resin is dissolved into the developing solution in the developer tank, thereby prolonging the life of the developing solution and enabling to increase the number of plates that can be developed by a predetermined amount of the developing solution.